I have a question regaurding the Pyruvate Dehydrogenase reaction. I have a Bioch

Question

I have a question regaurding the Pyruvate Dehydrogenase reaction. I have a Biochemistry exam next week and I am trying to understand the three enzymatic activities and 5 co-enzymes of the pyruvate dehydrogenase reaction. I tried following my professors notes, but I am getting confused by exactly what the cofactors are. I think the first one is thiamine pyrophosphate, which attacks pyruvate and removes a carbon dioxide molecule. What comes after this? That is, what are the four remaining enzymes? Thanks in advance!

Explanation / Answer

The Pyruvate Dehydrogenase complex links glycolysis to the TCA cycle( also known as kerbs cycle ).

THe oxidation of pyruvate occurs in the mitochondria of the cell. It is considered the 'power house' of the cell.

The three enzymes are:

1. E1 Pyruvate dehydrogenase which uses Thiamine pyrophosphate(TPP) as its prosthetic group.

2.E2 Dihydrolipoyl transacetylase which uses Lipoamide and coenzyme A.

3.E3 Dihydrolipoyl dehydrogenase which uses Flavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide( NAD+) as its cofactors.

2 pyruvate + 2NAD+ + 2coA----- 2acetyl coA + 2NADH + 2CO2

The Three principal enzyme

Pyruvate dehydrogenase(E1) or Pyruvate decorboxylase

Dihydrolipoyl transacetylase(E2)

Dihydrolipoyl dehydrogenase(E3)

Five coenzymes are

1.Thiamine pyrophosphate

2.Lipoic acid

3.Coenzyme A

4.Flavin adenine dinucleotide

5.Nicotinamide adenine dinucleotide we consider two pyruvates that enter from glycolysis and oxidation as follows:

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